Former Mayor Ray Nagin of New Orleans was found guilty on Wednesday of accepting payoffs for city contracts, becoming the first mayor in the city's history to be charged and convicted of corruption.

The jury deliberated for about 6 1/2 six hours in total before finding Nagin, 57, the Democratic mayor for two terms and the face of the city's leadership during the Hurricane Katrina disaster, guilty in 20 of the 21 counts against him.

Tania Tetlow, a Tulane University law professor and a former federal prosecutor, said Nagin could be facing 20 years or more under federal sentencing guidelines. He will remain free on bond until sentencing, but was placed on home detention.

The verdict came after a seven-day trial, during which more than 30 witnesses testified, including some businessmen who had pleaded guilty to bribing Nagin in return for contracting work with the city.

The most compelling days of the trial, and the ones that filled a courtroom that was half-empty most of the time, were those when Nagin himself took the stand, sparring with the prosecutor and dismissing the charges against him as misleading and misinformed.

With multiple witnesses and an extensive paper trial, federal prosecutors described a sequence of transactions between the mayor and various business interests, all following a similar pattern. The owner of a company would be trying to get city work, and would at some point make contact with Nagin. Nagin would ask for a favor, often in the form of payments to the granite countertop business Nagin ran with his two sons.

Nagin had argued that the payments were legitimate investments in the granite business, which he said was managed and run by his sons, with himself as a passive investor. He said the contracting process was largely out of his hands, awarded either by a public bid process or selected by a special committee.

This hands-off argument was undercut by e-mails and testimony tying Nagin directly to some deals.